1. Field of the Invention
The present invention relates to an engine control system with a vehicle anti-theft function, and particularly to an engine control system with a vehicle anti-theft function in which the start-up of the engine is enabled on the condition that a predetermined relationship is satisfied by an ID code previously registered in the ignition key or the like and another ID code previously registered on the vehicle body.
2. Description of the Prior Art
In some of the various proposals for preventing the theft of a vehicle such as a car, the vehicle is prevented from being started or it is immobilized by mechanical and/or electrical means when it is attempted to be started or moved using a wrong ignition key. This is achieved by previously storing an identification code or a key ID code in an ignition key, reading the key ID code when the key is inserted into a key cylinder to start up the engine, comparing it with a reference ID code prestored in the vehicle, and generating an enable signal and enabling the engine to be started up only when there is a match between both ID codes. In this case, since a theft may be committed by mechanical breakage or illegal re-wiring if the enable signal is a binary signal of on/off, the encoding of the enable signal has been proposed, for instance, in the "Car Technology", Vol. 48, No. 8, 1994, pp. 59-64.
An example of such a conventional transponder type immobilizer is shown in FIG. 6. An ignition key 2 includes a memory (not shown) in which a key ID code (for instance, of 64 bits) is prestored, and a transmitter 4 for transmitting the key ID code. The transmitter 4 of the key 2 and a key cylinder 5 are coupled together by, for instance, an induction coil (antenna) 6.
When the ignition key 2 is inserted into the key cylinder and rotated to the ignition ON position, an ignition switch 7 is closed. In response to this, an immobilizer CPU 13 in an IMMOBI-HIC 10 (hybrid IC for controlling the immobilizer) operates, and an operating electric power is supplied from the IMMOBI-HIC 10 to the transmitter 4 through an I/F (interface) 12, an antenna unit 19 and the coil (antenna) 6. The antenna unit 19 is electrically connected to the IMMOBI-HIC 10 along with the ignition switch 7 (and a battery 21) through a pair of connectors 40a and 50a. The transmitter 4 responds to the power supply to read the key ID code, and transmits it to the key cylinder 5 side.
The received key ID code is amplified in the antenna unit 19, read into the immobilizer CPU 13 and temporarily stored in an appropriate ID code register 13B in the CPU 13. In an EEPROM 14 of the IMMOBI-HIC 10, a unique reference ID code assigned to each vehicle is prestored, and the reference ID code and the key ID code which was read in are compared with each other by a compare unit 13S of the CPU 13. If it is determined that there is a match between the two ID codes or they are in a predetermined relationship, an enable code or a code signal is transmitted from the compare unit 13S to an engine control unit (engine CPU) 16. At the same time, a starter relay is activated to initiate the rotation of a starter motor (not shown).
The ECU 30 comprises a power supply 11, an engine CPU 16 and a ROM 15. The IMMOBI-HIC 10, fuel injection valve 17, fuel pump 18, ignition control unit 20 and battery 21 and others are electrically connected with each other through a pair of connectors 40a, 50a, and 40b, 50b.
In a ROM 15 of the engine ECU 30, an engine control program is stored which includes at least an engine control algorithm, an I/O (Input/Output) control algorithm and an anti-theft algorithm. The engine CPU 16 operates according to the engine control program, and discriminates or verifies the reception of the enable code on the basis of the anti-theft algorithm. If the enable code is correct code data, the engine CPU 16 performs a predetermined control based on the engine control algorithm for the respective terminal devices such as the fuel injection valve 17, the fuel pump 18 and the ignition control unit 20 connected to the signal port selected by the I/O control algorithm, thereby to enable the start and running of the vehicle.
If the reference ID code stored in the EEPROM 14 and the key ID code transmitted from the ignition key 2 and read in do not match each other or they are not in a predetermined relationship, the compare function unit 13S does not issue an enable code. Accordingly, the start of the vehicle by the CPU 16 is inhibited, and a horn (not shown) is activated by the immobilizer CPU 13 to provide an appropriate alarm and display.
When the enable code or code signal S1 transmitted from the compare unit 13S is not correct code data, the start of the vehicle by the engine CPU 16 is also inhibited. Thus, the Illegal start-up of the engine and the driving of the vehicle by a wrong key are prevented to ensure the vehicle anti-theft function.
In the foregoing prior art, electrical connection between the ECU 30 and the battery 21 is held by a mechanical contact between connector members of the connectors 40b and 50b. Accordingly, in case, for example, a vehicle wheel runs onto a side edge of the road, when large shock or vibration is exerted onto the vehicle, it is possible that the electrical connection in the connectors is disconnected momentarily to cause the engine to be stalled.
At this time, when the momentary disconnection of the electrical power occurs only relative to the ECU 30, and not relative to the other units, such as the IMMOBI-HIC 10, the ECU 30 is reset and starts over again the processes for the foregoing anti-theft determination. However, since the power disconnection has not occurred in the IMMOBI-HIC 10, a sequence of the processes for the anti-theft determination, for example, outputting of the code signal S1 for the correctness determination is not performed.
Accordingly, even if a driver turns the ignition switch from an ON position to a START position to restart the engine, the ECU 30 cannot receive the code signal S1 to be sent from the IMMOBI-HIC 10. As a result, the ECU 30 determines that an illegitimate or wrong engine key is being used, and thus prohibits the engine control. For enabling the engine control, the driver is required to first return the ignition switch to an OFF position to cause the IMMOBI-HIC 10 and the like to recognize the power disconnection, and thereafter, to perform again the engine start-up operation so as to allow a sequence of the anti-theft determination processes to be executed from the beginning.